Combined treatment method for copper anode slime and lead anode slime

Abstract

The invention relates to the technical field of non-ferrous metal smelting, and discloses a combined treatment method of copper anode slime and lead anode slime, which comprises the following steps: step 1, pretreatment: mixing the copper anode slime and the lead anode slime, and then sequentially carrying out ball-milling crushing and water-washing desalination, the ball-to-material ratio of the ball-milling crushing is 4: 1-6: 1, and the particle size D50 of the crushed material is 8-25 [mu] m; the pretreated raw materials and a leaching agent are mixed and react for 1.5-3 h at the temperature of 60-75 DEG C under ultrasonic field and constant potential control, the potential range of constant potential control is 0.90-1.10 V, and the leaching agent comprises, by mass, 35-45 parts of thiourea, 8-12 parts of sodium chloride, 4-6 parts of ammonium persulfate, 3-5 parts of citric acid and 12-18 parts of sulfuric acid. By adopting the technical scheme of the synergistic effect of electrochemical potential gradient regulation and control and a complexing competitive mechanism, the defect that the leaching rate of precious metal is insufficient due to overlapping of oxidation-reduction potentials is overcome.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal smelting, and in particular to a combined treatment method for copper anode slime and lead anode slime. Background Art

[0002] In the resource utilization of copper / lead anode mud, precious metal recovery is a key link, mainly using pyrometallurgy and wet leaching processes.

[0003] Pyrometallurgy, exemplified by Kaldo furnace smelting, offers high throughput but also extremely high energy consumption (>1500kWh per ton of material) and severe precious metal dispersion losses (Au recovery <90%). High temperatures also easily generate volatile toxic substances such as As₂O₃ and Sb₂O₃, requiring complex exhaust gas purification systems.

[0004] Wet leaching has turned to non-cyanide systems, represented by thiourea leaching, but there are many bottlenecks. The selective separation efficiency is low because the oxidation potential is difficult to accurately control, resulting in the overlap of the oxidation potentials of precious metals and base metals. Excessive oxidants cause the co-dissolution of base metals (Pb co-dissolution rate > 30%), which requires subsequent multi-stage purification. The process is complicated and costly. In terms of kinetics, the precious metals in the anode mud are wrapped, and traditional mechanical crushing (D50 > 50μm) does not fully expose the reaction interface. The diffusion boundary layer limits the speed. In order to increase the leaching rate, excessive thiourea is added (unit consumption 8-10kg / t), but thiourea is easily decomposed under acidic and high temperature (decomposition rate > 40%), resulting in serious waste of reagents. The risk of secondary pollution is high. There is a lack of solidification means for toxic elements such as arsenic and antimony in the leaching residue (As content 3-10wt%). The rainwater leaching amount (TCLP test As leaching amount > 12mg / L) far exceeds the standard (1mg / L), and there is excessive Cl in the leachate. - 、SO4 2- Emissions pollute the environment. Comprehensive resource utilization is insufficient, with the recovery rate of rare metals such as selenium and tellurium less than 20%. Landfill disposal of by-products fails to achieve high-value conversion. The recycling rate of thiourea is low (<30%), and the cost of reagents is high.

[0005] Despite attempts at partial improvements, such as microwave-assisted treatment, the dilemma of high energy consumption, low efficiency, and severe pollution persists, and the fundamental issues of competitive dissolution between precious and base metals remain unresolved. Therefore, the development of anode slime combined treatment technologies that combine high selectivity, low environmental impact, and closed-loop resource recycling is urgently needed. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention provides a combined treatment method for copper anode mud and lead anode mud, which solves the problem that the metal co-dissolution requires subsequent multi-stage purification, resulting in complex processes and high costs.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a method for jointly treating copper anode slime and lead anode slime, comprising the following steps:

[0008] Step 1: Pretreatment: Copper anode slime and lead anode slime are mixed and then subjected to ball milling and water washing and desalination in sequence. The ball-to-material ratio of the ball milling is 4:1 to 6:1, and the particle size D50 of the material after milling is 8 to 25 μm.

[0009] Step 2, leaching treatment: mixing the pretreated raw material with a leaching agent, reacting at 60-75° C. for 1.5-3 hours under ultrasonic field and constant potential control, wherein the potential range of the constant potential control is 0.90-1.10 V, and the leaching agent comprises, by mass, 35-45 parts of thiourea, 8-12 parts of sodium chloride, 4-6 parts of ammonium persulfate, 3-5 parts of citric acid, and 12-18 parts of sulfuric acid;

[0010] Step 3, solid-liquid separation: filtering the slurry after the reaction through a vacuum drum filter at a filtration pressure of -0.07 MPa to -0.12 MPa to obtain a leachate containing precious metals and a filter residue containing lead, antimony and arsenic;

[0011] Step 4: Recovery of precious metals: Adsorption of coconut shell activated carbon and diaphragm electrolysis are used to recover gold and silver from the leachate. The current density of the electrolysis is 80-180 A / m 2 .

[0012] Preferably, the rotation speed of the ball mill in step 1 is 250-450 rpm, and the grinding time is 2-4 hours.

[0013] Preferably, the frequency of the ultrasonic field in step 2 is 25-30 kHz, and the power density is 40-60 W / L.

[0014] Preferably, the potential fluctuation amplitude of the constant potential control in step 2 is ≤±20mV.

[0015] Preferably, the stirring rate in step 2 is 200-400 rpm.

[0016] Preferably, the pore size of the filter cloth in step three is 3 to 10 μm.

[0017] Preferably, the particle size of the coconut shell activated carbon in step 4 is 80-200 mesh, and the adsorption temperature is 20-40°C.

[0018] Preferably, the anode of the diaphragm electrolytic cell in step 4 is an IrO2-coated titanium mesh, and the cathode is a stainless steel plate.

[0019] Preferably, the liquid-to-solid ratio of the water washing desalination in step 1 is 3:1 to 5:1, the water washing temperature is 40 to 60° C., and the water washing time is 1 to 2 hours.

[0020] The present invention provides a combined treatment method for copper anode slime and lead anode slime, which has the following beneficial effects:

[0021] 1. The present invention achieves the technical effect of highly selective separation of precious metals (Au, Ag) and base metals (Pb, Sb, As) by adopting the technical solution of electrochemical potential gradient control and complex competition mechanism. Compared with the technical solution in the prior art that relies on a single oxidant (such as H2O2) or excessive acid leaching to cause a high metal co-solubility rate, it solves the defects of insufficient precious metal leaching rate (Au leaching rate of traditional process <85%) and base metal contamination of leachate (Pb co-solubility rate >30%) caused by the overlap of redox potential. By dynamic potential control (0.90-1.10V) and thiourea-Cl - The double coordination system increases the Au leaching rate to over 98.5% and reduces the Pb co-dissolution rate to below 5%.

[0022] 2. The present invention breaks through the bottleneck of slow mass transfer rate and long reaction time in traditional leaching process by adopting the technical scheme of ultrasonic field-mechanical activation synergistic pretreatment and diffusion boundary layer dynamic optimization. Compared with the technical scheme in the prior art that only relies on mechanical stirring or a single energy field (such as microwave), it solves the low reaction efficiency caused by the failure of the passivation layer to break through (the traditional process requires more than 6 hours). Through the synergistic effect of ultrasonic cavitation effect (25-30kHz) and ball milling to micron-level particle size (D50 = 8-25μm), the diffusion layer thickness can be reduced from 10 -4 m down to 10 -6 m, the reaction time is shortened by 40%, and the thiourea consumption is reduced to 2.5kg / t.

[0023] 3. This invention utilizes a citric acid buffer system combined with mineral phase reconstruction and solidification to achieve near-zero emissions of heavy metal pollutants and high-value byproducts. Compared to existing technologies that directly neutralize and discharge or simply landfill, this solves the problems of excessive As / Sb toxicity leaching (traditional filter residue As leaching volume >12mg / L) and resource waste. By inhibiting colloid formation through citric acid chelation (turbidity NTU <15) and immobilizing As / Sb with a Ca-Fe-SiO2 mineralizer (TCLP leaching volume <0.5mg / L), the invention simultaneously produces selenium and tellurium quantum dots (quantum yield 45%), converting environmental costs into value-added benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the combined treatment method of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Please see the attached Figure 1 The embodiment of the present invention provides a method for jointly treating copper anode slime and lead anode slime, comprising the following steps:

[0027] Step 1: Pretreatment: Copper anode mud and lead anode mud are mixed and then subjected to ball milling and water washing and desalination in sequence. The ball-to-material ratio of the ball milling is 4:1-6:1, and the particle size D50 of the material after milling is 8-25 μm.

[0028] Step 2, leaching treatment: mixing the pretreated raw material with a leaching agent, reacting at 60-75° C. for 1.5-3 hours under ultrasonic field and constant potential control, the potential range of the constant potential control is 0.90-1.10 V, and the leaching agent comprises, by weight, 35-45 parts of thiourea, 8-12 parts of sodium chloride, 4-6 parts of ammonium persulfate, 3-5 parts of citric acid, and 12-18 parts of sulfuric acid;

[0029] Step 3, solid-liquid separation: filtering the slurry after the reaction through a vacuum drum filter at a filtration pressure of -0.07 to -0.12 MPa to obtain a leachate containing precious metals and a filter residue containing lead, antimony and arsenic;

[0030] Step 4: Precious metal recovery: Coconut shell activated carbon adsorption and diaphragm electrolysis are used to recover gold and silver from the leachate. The current density of electrolysis is 80-180A / m 2 .

[0031] In step 1, the ball milling speed is 250-450 rpm, and the grinding time is 2-4 hours.

[0032] In step 2, the frequency of the ultrasonic field is 25-30 kHz, and the power density is 40-60 W / L.

[0033] The potential fluctuation amplitude of the constant potential control in step 2 is ≤±20mV.

[0034] The stirring rate in step 2 is 200-400 rpm.

[0035] In step 3, the pore size of the filter cloth is 3 to 10 μm.

[0036] In step 4, the particle size of the coconut shell activated carbon is 80-200 mesh, and the adsorption temperature is 20-40°C.

[0037] In step 4, the anode of the diaphragm electrolytic cell is an IrO2-coated titanium mesh, and the cathode is a stainless steel plate.

[0038] In step 1, the liquid-to-solid ratio of water washing desalination is 3:1 to 5:1, the water washing temperature is 40 to 60° C., and the water washing time is 1 to 2 hours.

[0039] Example:

[0040] Example 1:

[0041] Leaching agent formula: thiourea 38%, sodium chloride 10%, ammonium persulfate 5%, citric acid 4%, sulfuric acid 18%, water 25%.

[0042] step:

[0043] Step 1, pretreatment: copper / lead anode mud (mass ratio 1:1) was mixed and ground using a planetary ball mill with a ball-to-material ratio of 5:1 and a rotation speed of 380 rpm for 3.2 hours to obtain a D50 = 12 μm powder. 60 ° C deionized water was added at a liquid-to-solid ratio of 4:1, and the mixture was stirred at a speed of 300 rpm for 1.2 hours. The soluble sulfate was removed by filtration;

[0044] Step 2, leaching treatment: the pretreated material and the leaching agent were mixed at a solid-liquid ratio of 1:6, transferred to a Hastelloy alloy reactor, turned on 28kHz ultrasound (power density 55W / L, pulse mode: 12s on / 6s off), constant potential control 1.02V (vs. SHE), maintained at 68°C, stirring rate 320rpm, and reacted for 2.4h;

[0045] Step 3, solid-liquid separation: vacuum drum filtration (-0.09 MPa, filter cloth pore size 6 μm), the filter residue was detected by XRD to contain PbCl2 (94.3%) and Sb2O3 (5.1%);

[0046] Step 4: precious metal recovery: the leachate is passed through 120 mesh coconut shell activated carbon (25℃ adsorption for 3h), the gold-loaded carbon is incinerated and electrolyzed to obtain Au with a purity of 99.95%; electrolysis regenerates thiourea (IrO2 / Ti anode, current density 135A / m 2 ), the leaching rate is still >97% after three cycles.

[0047] Example 2:

[0048] Leaching agent formula: thiourea 42%, sodium chloride 9%, ammonium persulfate 6%, citric acid 3%, sulfuric acid 16%, water 24%.

[0049] step:

[0050] Step 1: Pretreatment: Lead anode mud accounts for 70%, ball mill parameters: ball-to-material ratio 4.5:1, speed 420 rpm, crushing for 2.8 hours, D50 = 18 μm, liquid-to-solid ratio 3:1, 45°C water washing for 0.8 hours, remove 72% of soluble lead salts;

[0051] Step 2, leaching treatment: solid-liquid ratio 1:5, ultrasonic frequency 26 kHz (continuous mode, power density 48 W / L), constant potential 0.98 V (vs. SHE), temperature 63°C, reaction time 3 h, stirring at 250 rpm;

[0052] Step 3, solid-liquid separation: The filter cloth has a pore size of 4 μm, and the filter residue TCLP test shows that the As leaching amount is 0.3 mg / L (lower than the national standard of 1 mg / L);

[0053] Step 4: precious metal recovery: activated carbon adsorption (35°C, 4h), Ag recovery rate 99.1%, electrolytic regeneration efficiency 92%, thiourea decomposition rate <5%.

[0054] Example 3:

[0055] Leaching agent formula: thiourea 35%, sodium chloride 12%, ammonium persulfate 4%, citric acid 5%, sulfuric acid 20%, water 24%.

[0056] step:

[0057] Step 1: Pretreatment: Copper anode mud accounts for 80%, planetary ball milling (speed 300 rpm, time 4h) to D50 = 8μm, liquid-solid ratio 5:1, 55℃ water washing for 1.5h to remove 89% of CuSO4;

[0058] Step 2: Leaching treatment: solid-liquid ratio 1:7, 30 kHz ultrasound (power density 60 W / L, pulse 10 s / 5 s), constant potential 1.05 V (vs. SHE), temperature 72°C, reaction 1.8 h, stirring 380 rpm;

[0059] Step 3: Solid-liquid separation: The Pb content in the filter residue is 22.4% (XRF analysis), which can be directly sent to lead smelting for recovery;

[0060] Step 4: Precious metal recovery: diaphragm electrolysis (cathode current efficiency 94%), power consumption per ton of anode mud is 810kWh, waste liquid is treated by TiO2 / MoS2 photocatalysis, and cyanide degradation rate is >99.9%.

[0061] Example 4:

[0062] Leaching agent formula: thiourea 45%, sodium chloride 8%, ammonium persulfate 5%, citric acid 4%, sulfuric acid 15%, water 23%.

[0063] step:

[0064] Step 1: Pretreatment: Copper / lead anode mud was mixed at a ratio of 2:1, ball milled to D50 = 22 μm (ball-to-material ratio 6:1, rotation speed 260 rpm, 3.5 h), liquid-to-solid ratio 2:1, washed with water at 50 ° C for 2 h, and the desalination rate was 81%;

[0065] Step 2, leaching treatment: solid-liquid ratio 1:4, ultrasound 25 kHz (power density 45 W / L), constant potential 0.93 V (vs. SHE), temperature 75°C, reaction time 2.1 h, stirring rate 400 rpm;

[0066] Step 3: Solid-liquid separation: After the filter residue is solidified with CaO, the As leaching amount is 0.2 mg / L, which meets the landfill standard;

[0067] Step 4: Precious metal recovery: The gold loading capacity of activated carbon adsorption reaches 8.2 g / kg. After electrolytic purification, the Au purity is 99.99%. The selenium content of the leaching solution is 0.7 g / L, and Se / Te nanoparticles can be co-produced.

[0068] Comparative Example:

[0069] Comparative Example 1: Leaching agent formulation and potential control corresponding to Example 1

[0070] The leaching agent formula was adjusted to: 20% thiourea, 20% sodium chloride, 10% ammonium persulfate, 25% sulfuric acid, and 25% water (no citric acid added).

[0071] Step adjustment:

[0072] Leaching treatment: without controlling the potential, directly adding excess H2O2 (3 mol / L) as an oxidant; without ultrasonic field, only mechanical stirring (300 rpm), temperature 80 ° C, reaction time 4 h.

[0073] Comparative Example 2: Pretreatment and ultrasonic parameters corresponding to Example 2

[0074] The leaching agent formula remains unchanged: leaching agent formula: thiourea 42%, sodium chloride 9%, ammonium persulfate 6%, citric acid 3%, sulfuric acid 16%, water 24%.

[0075] Step adjustment:

[0076] Pretreatment: Lead anode mud was directly crushed to D50 = 150 μm without ball milling; water washing and desalination conditions: liquid-solid ratio 1:1, stirring at room temperature (25°C) for 0.5 h.

[0077] Leaching treatment: ultrasonic frequency 40 kHz, power density 80 W / L (continuous mode, no pulse); constant potential control 1.20 V, exceeding the Au / Pb oxidation potential difference range.

[0078] Comparative Example 3: pH buffering and post-treatment corresponding to Example 3

[0079] The leaching agent formula was adjusted to: thiourea 35%, sodium chloride 12%, ammonium persulfate 4%, phosphoric acid 5%, sulfuric acid 20%, and water 24%.

[0080] Step adjustment: solid-liquid separation: filter residue is directly piled up without solidification treatment;

[0081] Precious metal recovery: Zinc powder replacement method was used instead of activated carbon adsorption (zinc powder dosage 8g / L); no diaphragm was used during electrolytic regeneration of thiourea.

[0082] Comparative Example 4: Mixed Anode Mud Treatment and Equipment Selection Corresponding to Example 4

[0083] The leaching agent formula remains unchanged: thiourea 45%, sodium chloride 8%, ammonium persulfate 5%, citric acid 4%, sulfuric acid 15%, water 23%.

[0084] Step adjustment: Raw material processing: only process single copper anode mud (not mixed with lead anode mud);

[0085] Reactor material: 304 stainless steel, not Hastelloy C276;

[0086] Leaching conditions: potential was not controlled, reaction temperature was 90°C; stirring rate was 100 rpm, and the diffusion layer thickness was increased to 50 μm.

[0087] Comparative experiment:

[0088] Experiment 1: Leaching agent formulation and potential control effect verification

[0089] Comparative group: Example 1 vs. Comparative Example 1

[0090] Test parameters: Au leaching rate, Pb co-dissolution rate, thiourea consumption

[0091] Experimental steps: Raw material pretreatment: Copper anode mud (Au 1.0wt%) and lead anode mud (Au 0.5wt%) were mixed in a mass ratio of 1:1 and ball-milled to D50 = 12μm; liquid-solid ratio 4:1, washed and desalted at 60℃ for 1.2h to remove soluble sulfate.

[0092] Leaching reaction:

[0093] Example 1: Leaching agent formula: thiourea 38%, sodium chloride 10%, ammonium persulfate 5%, citric acid 4%, sulfuric acid 18%, water 25%;

[0094] The constant potential was controlled at 1.02 V (vs. SHE), the temperature was 68°C, there was no ultrasonic field, and the reaction time was 2.4 h.

[0095] Comparative Example 1: Leaching agent formula: thiourea 20%, sodium chloride 20%, H2O2 10%, sulfuric acid 25%, water 25%;

[0096] There was no potential control, the temperature was 80 °C, the reaction time was 4 h, the solid-liquid ratio was uniformly 1:6, and the stirring rate was 300 rpm.

[0097] Solid-liquid separation:

[0098] After the reaction was completed, vacuum filtration (-0.09 MPa, filter cloth pore size 6 μm) was performed to collect the leachate and filter residue.

[0099] Detection and analysis: ICP-OES was used to determine the concentrations of Au and Pb in the leachate; the UV-Vis method (240 nm wavelength) was used to determine the residual amount of thiourea and calculate the consumption.

[0100] The experimental data are shown in the following table:

[0101] Table 1: Comparison of leaching agent formulation and potential control data

[0102]

[0103] Experimental summary:

[0104] The introduction of mixed potential theory significantly changes the oxidation priority of the multimetallic system. - -APS ternary system accurately matches the oxidation window of Au (0.8-1.0V) through dynamic potential control (1.02V), while the strong oxidizing property of H2O2 (Comparative Example 1) causes potential loss of control (measured to rise above 1.3V), triggering the dissolution of Pb (E 0 =1.4V). Thiourea concentration gradient distribution (38% vs 20%) and Cl - The precipitation effect (Ksp, PbCl2 = 1.6 × 10 -5 ) form a competitive barrier, inhibiting the migration of base metal ions into the solution phase.

[0105] The destruction of the diffusion boundary layer is reflected in the cliff-like difference in thiourea consumption. In the comparative example 1, there is no ultrasonic field and the temperature is too high (80°C). The thiourea molecules lose their complexing ability due to thermal decomposition and the formation of disulfide formamidine by-products (UV-Vis detection of the absorption peak shift at 240nm). 3+ (logβ=12.3), thus avoiding the mass transfer obstruction of Au by colloid encapsulation and increasing the effective utilization rate of thiourea to 89%.

[0106] The irreversibility of the potential-ligand coupling mechanism further magnifies the performance gap between the two groups. - (20%) can precipitate Pb 2+However, high concentration of H2O2 triggers a free radical chain reaction (·OH generation), which accelerates the oxidative degradation of thiourea. - The Au / thiourea molar ratio (0.26) was optimized by the Levich equation, and the selective dissociation of Au was achieved at the critical diffusion layer thickness (δ = 1.2 μm), ultimately resulting in a subversive result of a leaching rate of >98% and a Pb co-dissolution rate of <5%.

[0107] Experiment 2: Pretreatment particle size and ultrasonic parameter optimization verification

[0108] Comparative group: Example 2 vs. Comparative Example 2

[0109] Test parameters: reaction rate, lead content in filter residue

[0110] Experimental steps:

[0111] Raw material sorting and pretreatment:

[0112] Example 2: Lead anode slime (Ag 5.2 wt%) was treated by planetary ball milling (rotation speed 420 rpm, ball-to-material ratio 4.5:1) for 2.8 h to obtain a powder with an average particle size D50 = 18 μm; then, 45°C deionized water was added at a liquid-to-solid ratio of 3:1 and stirred for desalination for 0.8 h.

[0113] Comparative Example 2: The same lead anode slime was only coarsely crushed to D50 = 150 μm by a jaw crusher without ball milling; the water washing conditions were a liquid-to-solid ratio of 1:1 and stirring at room temperature (25°C) for 0.5 h.

[0114] Leaching reaction configuration: Both groups used the leaching agent formula of Example 2 (thiourea 42%, sodium chloride 9%, ammonium persulfate 6%, citric acid 3%, sulfuric acid 16%, water 24%), with a solid-liquid ratio of 1:5;

[0115] Example 2: A 26kHz piezoelectric ultrasonic transducer was integrated in the leaching tank, in pulse mode (working for 12s / pausing for 5s), with a power density of 48W / L;

[0116] Comparative Example 2: A 40kHz commercial ultrasonic cleaner (continuous output, power density 80W / L) was used without pulse control;

[0117] The constant potential was uniformly set at 0.98 V (vs. SHE), the temperature was 63° C., the mechanical stirring rate was 250 rpm, and the reaction time was 3 h.

[0118] Endpoint determination and sampling: 5 mL of the extract was collected every 30 min, centrifuged, and the supernatant was diluted 10 times for kinetic analysis. After the reaction, the filter residue was vacuum dried (60°C, 4 h), ground, and packaged for testing.

[0119] Detection method: Kinetic curve: Determine the Au concentration by ICP-OES and calculate the instantaneous leaching rate (mg / (L·min));

[0120] Filter residue composition: Semi-quantitative analysis of lead and antimony oxide content by X-ray fluorescence spectroscopy (XRF);

[0121] Micromorphology: Five filter residue samples were randomly selected and the surface porosity was observed by SEM (statistics using ImageJ software).

[0122] The experimental data are shown in the following table:

[0123] Table 2: Effects of particle size and ultrasonic parameters on the reaction

[0124]

[0125] Experimental summary:

[0126] The difference in raw material particle size directly reconstructs the reaction topology of the solid-liquid interface. The ball milling pretreatment of Example 2 (D50 = 18 μm) increased the specific surface area by nearly 3 times (BET test increased from 0.8 to 2.7 m 2 / g), while the coarse particles (Comparative Example 2, D50 = 150μm) have difficulty penetrating thiourea molecules into the precious metal coating due to the surface energy barrier. The 38% porosity in the SEM image provides a micro-region for the collapse of ultrasonic cavitation bubbles, where local transient high pressure (~100MPa) shatters the PbCl2 passivation film. This mechanism is blocked by the dense surface of Comparative Example 2 (porosity <14%).

[0127] The shift in ultrasonic frequency triggers energy dissipation at the molecular scale. The 26kHz pulse field in Example 2 forms a stable cavitation cloud in the liquid phase. The bubble collapse time (~2μs) matches the diffusion relaxation time of thiourea molecules (~1.5μs), which strengthens the [Au(TU)2] + The desorption process of the complex. However, the 40kHz continuous ultrasound in the comparative example 2 resulted in too high a cavitation bubble density, and the excessive free radicals (·OH) attacked the C=S bond in the thiourea molecule (FTIR detected 1710cm -1 The characteristic peak attenuated at the bottom of the column, part of the thiourea oxidation failed, and the peak leaching rate was suppressed below 1.5 mg / (L·min).

[0128] The synergistic effect of particle size and ultrasound further amplifies the efficiency of lead inhibition. - The adsorption energy on the surface of micron-sized Pb particles (-1.8 eV calculated by DFT) promotes the rapid nucleation of PbCl2. XRF shows that the lead content of the filter residue is stable at around 22%. However, in the comparative example 2, the millimeter-sized lead particles have insufficient reaction interface, and a large amount of Pb 2+ Breakthrough Cl -The precipitation barrier enters the solution (cosolubility>65%). The nonlinear relationship between porosity and mass transfer rate (fitting R 2 =0.93) shows that when D50 is less than 25 μm, the thinning effect of the ultrasonic field on the diffusion boundary layer (δ decreases from 12 μm to 0.8 μm) becomes the key to controlling the speed, while the particle size threshold of comparative example 2 far exceeds this range, and the dynamic advantage disappears.

[0129] Experiment 3: pH buffering and post-treatment environmental verification

[0130] Comparative group: Example 3 vs. Comparative Example 3

[0131] Test parameters: Sb colloid generation, As leaching toxicity

[0132] Experimental steps:

[0133] Raw material pretreatment:

[0134] Example 3: Copper anode slime (As 4.3 wt%) was treated by planetary ball milling (rotation speed 300 rpm, ball-to-material ratio 5:1) for 4 h to obtain D50 = 8 μm powder; liquid-to-solid ratio 5:1, 55 ° C water washing and desalination for 1.5 h to remove soluble copper sulfate.

[0135] Comparative Example 3: The same copper anode mud was crushed to D50=50 μm (jaw crusher), with a liquid-solid ratio of 3:1 and washed with water at room temperature (25°C) for 0.5 h.

[0136] Leaching system configuration:

[0137] Example 3: The leaching agent contained 5% citric acid, 35% thiourea, 12% sodium chloride, 4% ammonium persulfate, 20% sulfuric acid, and 24% water; the reaction was carried out at a constant potential of 1.05 V (vs. SHE), a temperature of 72° C., and 30 kHz ultrasound (pulse 10 s / 5 s) for 1.8 h.

[0138] Comparative Example 3: The leaching agent was replaced by an equal amount of phosphoric acid (5%) instead of citric acid, pH = 1.0 (adjusted by sulfuric acid), no potential control, reaction temperature 85° C., and conventional stirring (400 rpm).

[0139] Post-processing process:

[0140] Example 3: CaO and FeSO4 (mass ratio 1:2) were added to the filter residue, and the toxicity was tested after solidification for 2 hours;

[0141] Comparative Example 3: The filter residue was directly piled in the open air without solidification.

[0142] Detection method:

[0143] Turbidity analysis: After the extract has been allowed to stand for 30 minutes, the NTU value is measured using a portable turbidity meter;

[0144] As leaching test: The TCLP method (acetic acid buffer, pH = 2.88 ± 0.05) was used to shake the mixture for 18 h, and the As concentration in the filtrate was determined by ICP-MS.

[0145] Thiourea stability: HPLC (C18 column, acetonitrile / water = 30:70) was used to detect thiourea residues and decomposition products.

[0146] The experimental data are shown in the following table:

[0147] Table 3: Effects of pH buffering and solidification treatment on environmental performance

[0148]

[0149] Experimental summary:

[0150] The chelation effect of citric acid reconstructs the distribution pattern of metal ions at the microscopic scale. 3- ) and Sb 3+ The complex constant (logβ=8.7) is much higher than that of the phosphoric acid system (Comparative Example 3, logβ=2.1), forcing Sb 3+ In soluble form [Sb(CA)] - The phosphoric acid in comparative example 3 cannot effectively bind Sb 3+ , the hydrolysis products formed a colloidal network (NTU>350) in the leachate, which not only blocked the pores of the filter cloth but also wrapped the unreacted Au particles, causing the thiourea residual rate to plummet to below 40%.

[0151] The lack of a solidification process directly triggered a chain reaction of environmental risks. The untreated filter residue in Comparative Example 3 released 15 mg / L of As (15 times the standard) in the TCLP test, while the CaO-FeSO4 solidifying agent in Example 3 removed As by chemical adsorption and co-precipitation. 30 The ore phase was fixed to stable scorodite (FeASO4·2H2O, with characteristic peaks PDF#72-1903 detected by XRD). The irreversibility of this mineral phase reconstruction (ΔG=-158 kJ / mol) blocked the As re-dissolution path, and the leaching concentration was suppressed to below 0.3 mg / L.

[0152] The difference in the stability of thiourea further reveals the hidden mechanism of pH regulation. The citric acid buffer system (pH = 1.5) in Example 3 inhibits the nucleophilic attack of H2O molecules on thiourea (the hydrolysis activation energy increases from 85kJ / mol to 112kJ / mol), and the thiourea residual rate is greater than 89%. + When the concentration is too high, thiourea is protonated to form [TUH] +(UV absorption red shift 12nm), accelerating its oxidative decomposition into disulfide formamidine (peak area at HPLC retention time 6.8min accounts for >55%), and ultimately causing the collapse of complexing ability.

[0153] Experiment 4: Mixed Raw Material Processing and Equipment Corrosion Resistance Verification

[0154] Comparative group: Example 4 vs. Comparative Example 4

[0155] Test parameters: comprehensive recovery rate of precious metals, Fe 3+ Pollution

[0156] Experimental steps:

[0157] Raw material ratio and pretreatment:

[0158] Example 4: Copper anode slime (Pb12.6wt%) and lead anode slime (Sb11.2wt%) were mixed in a mass ratio of 2:1 and subjected to planetary ball milling (ball-to-material ratio 6:1, speed 260rpm) for 3.5h to a D50 of 22μm; liquid-to-solid ratio 2:1, and desalination was performed by water washing at 50°C for 2h.

[0159] Comparative Example 4: Only copper anode mud (raw materials from the same batch) was processed, jaw crushed to D50 = 80 μm, liquid-solid ratio 1:1, and washed with water at room temperature (25° C.) for 0.5 h.

[0160] Leaching system construction:

[0161] Example 4: Hastelloy C276 reactor, leaching agent formula (thiourea 45%, sodium chloride 8%, ammonium persulfate 5%, citric acid 4%, sulfuric acid 15%, water 23%), solid-liquid ratio 1:4;

[0162] Comparative Example 4: 304 stainless steel reactor, thiourea concentration in the leaching agent formula was reduced to 30% (replaced with an equal amount of water), and the remaining components were the same as in Example 4;

[0163] The temperature of both groups was set at 75°C, the mechanical stirring was 400 rpm, the reaction time was 2.1 h, and no ultrasonic field was applied.

[0164] Post-treatment and analysis: The leachate was adsorbed on activated carbon (80-200 mesh coconut shell charcoal, adsorption at 35°C for 3 h), and the residual liquid was circulated to the electrolytic regeneration unit. The filter residue was solidified with CaO (Ca / As molar ratio 4:1) and tested for stability after shaking for 24 h.

[0165] Detection method:

[0166] Metal contamination detection: Atomic absorption spectroscopy (AAS) determination of Fe in leachate 3+ concentration;

[0167] Noble metal distribution: X-ray photoelectron spectroscopy (XPS) analysis of Au4f binding energy shift on the residue surface;

[0168] Equipment corrosion: Samples were taken from the inner wall of the reactor, and the pit depth and element distribution were analyzed using SEM-EDS.

[0169] The experimental data are shown in the following table:

[0170] Table 4: Influence of mixed raw materials and equipment materials on the system

[0171]

[0172]

[0173] Experimental summary:

[0174] The difference in corrosion resistance of equipment materials reconstructs the competition pattern of metal ions at the micro scale. - -H + Pitting corrosion occurs in the medium (corrosion current density 3.2×10 -5 A / cm 2 ), dissolved Fe 3+ (concentration>25mg / L) reacts with thiourea to form [Fe(TU)3] 3+ The complex (UV absorption peak red-shifted to 265nm) robs the free thiourea molecules in the solution, resulting in a 23% decrease in the Au complex capacity. However, the Hastelloy C276 alloy of Example 4 forms a stable MoO4 in the passivation film due to its Mo content of 15.5% (EDS surface scanning). 2- Protective layer (XPS binding energy 232.8eV), Fe 3+ The dissolution concentration is suppressed below 1 mg / L, ensuring the selectivity of thiourea for Au.

[0175] The introduction of mixed raw materials unexpectedly triggered the synergistic passivation effect of lead and antimony. In Example 4, the Sb2O3 (XRD detected PDF#05-0534) of the lead anode mud was - In the environment, it is converted into SbOCl (solubility product Ksp = 1.3×10 -10 ), its dense crystal structure (SEM shows layered stacking) covers the surface of the copper anode mud, blocking the dissolution path of As. However, the single copper mud in comparative example 4 lacks the passivation synergy of Sb, and As 30 It is dissolved in large quantities in the form of H3AsO3 (As concentration in the leachate is 8.7 mg / L), occupying the thiourea coordination site (DFT-calculated binding energy -2.1 eV), further deteriorating the recovery rate of precious metals.

[0176] The nonlinear coupling of corrosion and mass transfer amplifies the instability of the system. The pitting pit (depth>10μm) of comparative example 4 becomes a dead zone of eddy current, and the local Cl - The concentration soared to 2.3 mol / L (ICP test), triggering supersaturated precipitation of PbCl2 (particle size > 50 μm, clogging the filter cloth). In contrast, the Hastelloy alloy of Example 4 had a surface roughness of Ra = 0.8 μm (measured by white light interferometry). The microgroove structure induced a thinning of the laminar boundary layer (CFD simulation showed a 37% reduction in the flow velocity gradient), allowing uniform nucleation of PbCl2 in the form of nanocrystals (TEM showed a particle size of 5-8 nm), significantly improving filtration efficiency.

[0177] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for the combined treatment of copper anode slime and lead anode slime, characterized in that: The following steps are involved: Step 1: Pretreatment: Copper anode slime and lead anode slime are mixed and then subjected to ball milling and water washing and desalination in sequence. The ball-to-material ratio of the ball milling is 4:1 to 6:1, and the particle size D50 of the material after milling is 8 to 25 μm. Step 2, leaching treatment: mixing the pretreated raw material with a leaching agent, reacting at 60-75° C. for 1.5-3 hours under ultrasonic field and constant potential control, wherein the potential range of the constant potential control is 0.90-1.10 V, and the leaching agent comprises, by mass, 35-45 parts of thiourea, 8-12 parts of sodium chloride, 4-6 parts of ammonium persulfate, 3-5 parts of citric acid, and 12-18 parts of sulfuric acid; Step 3, solid-liquid separation: filtering the slurry after the reaction through a vacuum drum filter at a filtration pressure of -0.07 MPa to -0.12 MPa to obtain a leachate containing precious metals and a filter residue containing lead, antimony and arsenic; Step 4: Recovery of precious metals: Adsorption of coconut shell activated carbon and diaphragm electrolysis are used to recover gold and silver from the leachate. The current density of the electrolysis is 80-180 A / m 2 .

2. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: In the step 1, the rotation speed of the ball mill is 250-450 rpm, and the grinding time is 2-4 hours.

3. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: In the second step, the frequency of the ultrasonic field is 25-30 kHz, and the power density is 40-60 W / L.

4. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: The potential fluctuation amplitude of the constant potential control in step 2 is ≤±20mV.

5. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: The stirring rate in the step 2 is 200-400 rpm.

6. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: The pore size of the filter cloth in step 3 is 3 to 10 μm.

7. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: In the step 4, the particle size of the coconut shell activated carbon is 80-200 mesh, and the adsorption temperature is 20-40°C.

8. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: In the fourth step, the anode of the diaphragm electrolytic cell is an IrO2-coated titanium mesh, and the cathode is a stainless steel plate.

9. The method for combined treatment of copper anode slime and lead anode slime according to claim 1, characterized in that: In the step 1, the liquid-to-solid ratio of the water washing desalination is 3:1-5:1, the water washing temperature is 40-60° C., and the water washing time is 1-2 hours.

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